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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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This topic is about the Insect Family Corydalidae

Hellgrammites are the vicious larvae of the Dobsonflies, some of the only trout stream insects which pose a biting threat to the angler. The pincers of the adult are even more frightening that the larva's, and they're aggressive enough to use them once in a while.

This family's life cycle does not create good dry fly opportunities, but the larvae may be eaten by trout year-round. They are a secret told only by stomach samples of well-fed trout.

Example specimens

Gandoff
Posts: 1
Gandoff on Mar 9, 2007March 9th, 2007, 2:02 pm EST
I have been fly fishing a lot over the past two years in the mountains of NC and Va. I have pumped the contents of many trout, and 2 out of 3 times, I find Hellgrammites in large brown trout, 18"+. perhaps they are not as numerous as caddis', but nether are crawfish, and wild trout like to eat them too!
As noted on several other replies, the warm bridge, and warm rocks, if you want to reasearch Hellgrammites, this is a good place to start.
Troutnut
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Bellevue, WA

Posts: 2758
Troutnut on Mar 10, 2007March 10th, 2007, 3:23 am EST
Thanks for the insight!
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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